Thin laminated gasket

ABSTRACT

A thin gasket for high compression engines comprises two outer metal sheets of uniform thickness within a range of from 0.0055 to 0.0085 inch and a filler having a compressible section with a total thickness no greater than 0.015 inch. The compressible section of the filler may comprise one or two sheets of impregnated fibers, and if only one sheet is used, the filler may also include a thin metal shim of the same thickness as one of the outer sheets and is positioned between the upper surface of the filler sheet and the upper outer sheet. The bottom sheet has flanges bent over the outer edges of the upper sheet and they are compressed to provide a gasket of uniform thickness totaling less than 0.030 inch.

United States Patent I191 3,738,558 Colwell June 12, 1973 [54] THINLAMINATED GASKET FOREIGN PATENTS OR APPLICATIONS Inventor: g liil Mount955,215 Great Britain 277 235 B rospect,

[73] Assignee: Felt Products Mfg. Co., Skokie, Ill. Primary ExamnerR0bert I. Smith [2 Fi p 2 1970 Attorney-Dressler, Goldsmith, Clement& Gordon I [2]] App]. NO.I 68,935 57 ABSTRACT Related Application Data Athin gasket for high compression engines comprises [63]Continuation-impart of Ser. No. 756,908, Sept. 3, two outer metal sheetsof uniform thickness within a 1 abandoned, which is a n n-in-pa of rangeof from 0.0055 to 0.0085 inch and a filler having 9- 33 y 17, 1965,abandoned, which Is a compressible section with a total thickness nogreater a commuauomn'part of 385,747 July than 0.015 inch. Thecompressible section of the filler 1964 abandoned may comprise one ortwo sheets of impregnated fibers, and if only one sheet is used, thetiller may also include [22] a thin metal shim of the Same thickness asone of the B outer sheets and is positioned between the upper sur- 1 1e0 l face of the filler sheet and the upper outer sheet. The bottom sheethasflanges bent over the outer edges of [56] References cued the uppersheet and they are compressed to provide a UNITED STATES PATENTS gasketof uniform thickness totaling less than 0.030 1,823,341 9/1931 Victor277/235 B lIlCl'L' 2,029,302 2/1936 Balfe 277/235 B 0 2,034,610 3/1936Dickson 277/235 B 5 Claims, 9 Drawing Flgures I l I Patented June 121973 3,738,558

3 Sheets-Sheet l Patented June 12, 1973 3,738,558

3 Sheets-Sheet 2 I .Q JM/z7 Z; M, M2 2 jMlgfu wmeya June 12, 1973 3Sheets-Sheet 3 Patented THIN LAMINATED GASKET This application is acontinuation-in-part of Colwell application Ser. No. 756,908, filedSept. 3, 1968, now abandoned, which was a continuation-in-part ofColwell application Ser. No. 458,833, filed May 17, 1965, now abandoned,which was a continuation in part of Colwell application Ser. No.385,747, filed July 28, 1964, now abondoned, all of said applicationsbeing assigned to the assignee of the present invention.

This invention relates to a thin laminated gasket adapted to be usedbetween the cylinder block and the cylinder head of an engine to sealthe joints around the cylinder bores and fluid passages of said engine,and is particularly concerned with means for increasing the sealingefficiency and useful life of the gasket.

The invention will be described with particular reference to gaskets foruse in sealing the cylinder bores and fluid passages in high compressionengines, in which environment it has special advantages. Gaskets for usein sealing high compression engines, in addition to having all thequalities generally required in gaskets, should be oflimited thickness,i.e.-, not more than 0.030 inch, to assist in obtaining a highcompression ratio. The fibers used in the compressible filler sheets ofthe gasket of the present invention are dimensionally stable under thetemperature and pressure conditions encountered in a high compressionengine. Thus, they enable the filler sheets to be made of uniformthickness within the indicated range and .to substantially maintain thatthickness in use, thus making possible the making of the desired thingasket. This thin gasket provides a seal for the cylinder bores andfluid passage of a high compression engine, of an efficiency notobtainable with the gaskets of the prior art. It will be understood,however, that the invention is not limited to gaskets for use in highcompression engines, and that gaskets made in accordance with theinvention may be used in other environments in which they may haveutility.

It has been found that gaskets having a total compressed thickness ofmore than 0.030 inch are not commercially desirable for use in highcompression engines because they tend to reduce compression ratio ratherthan improve it, thereby reducing efficiency of such engines. Gaskets ofthe present invention provide for compression ratios much higher thanconventional gaskets without impairing the efficiency of the seal.Relatively thick gaskets previously available made of a combination ofmetal and asbestos sheets, which have been common in this art, have notproven to be entirely satisfactory for use in high compression engines.The gasket disclosed in Victor eta]. US. Pat. No. 2,130,110 is anexample of the prior art in which the gasket is made of a plurality ofmetal and asbestos sheets laminated together. The total thickness of agasket of this type is such as to render them commercially unacceptablefor use in a high compression engine. Thicker gaskets also have atendency to permit casting warpage because they cause the bolt pressureto be concentrated in the areas contiguous to the bolts, with a tendencyfor the gasket to gap in the areas between the bolts. The gaps in theedge of the gasket induce a bowing effect in the casting. The thingasket does not cause gaps in the gasket edges and thus avohds thebowing effect that induces casting warpage.

It has also been found that in gaskets having a thickness greater than0.030 inch, and particularly those wherein the compressible material ofthe gasket has a thickness greater than 0.015 inch, once the head hasbeen tightened to the block and the engine has been run for a period oftime, the relatively thick compressible material of the gasket has atendency to set, and it is necessary to retighten the bolts. Gasketsconstructed in accordance with the present invention, wherein themaximum thickness of the compressible section of the filler means is0.015 inch, have exhibited surprisingly good torque retention, and ithas been found that it is not necessary to retighten the bolts, evenafter extended periods of use.

In order to provide a gasket having a total compressed thickness of lessthan 0.030 inch, many automobile manufacturers have used embossed steelshims as gaskets. These embossed steel shims are inefficient as sealinggaskets for high compression engines because they depend entirely upondimensionallyprecise embossments and synthetic resin surface coatings onthese embossments to provide the seal. The seal is largely ineffectivewhenever there is any degree of irregularityin the finish of the matingcasting surfaces. Although the cost of a steel gasket is nominal, thecost of the labor required to replace one in service in considerable,and the usual critical condition of casting surfaces constitutes aserious objection to its use.

One embodiment of a gasket constructed in accordance with the presentinvention comprises compressible filler means sandwiched between twothin outer metal sheets. The outer metal sheets are of uniform thicknesswithin a range of from 0.0055 to 0.0085 inch, and the compressiblesection of the filler means has a total thickness no greater than 0.015inch. The filler means has no cold flow characteristics and willmaintain dimensional stability under the temperature and pressureconditions to which the gasket will be subjected in use in a highcompression engine.

The compressible section of the filler means may comprise one or twosheets, either woven or nonwoven, of fibers impregnated with a bindercapable of withstanding the action of water, ethylene glycol, alcohol,lubricating oils, steam, and radiator flush, at the temperature andpressure conditions that may be encountered when the gasket is usedbetween the cylinder block and the head of a high compression engine. Ingaskets comprising a single compressible filler sheet within the twoouter metal sheets, the filler means may include a thin metal shimbetween the compressible sheet and the top outer metal sheet. The metalshim is preferably coated with a cured thermosetting resin.

In another embodiment, the gasket has a single compressible filler sheetand the two outer metal sheets are secured together permanently,preferably be welding, in a plurality of spaced areas near the outeredges of the gasket. In this embodiment, the filler sheet is aperturedin each of the areas where the welds are to be located, and the outermetal sheets are indented to provide a metal-to-metal contact.

In a further embodiment, the filler means that is interposed between thetwo outer sheets is defined by a layer of impregnated fibers and a metalshim; and a plurality of projections are struck downwardly from theuppermost sheet and extend through the layer of fibers to preventlateral shifting between the uppermost sheet and the fiber layer.

In still another embodiment, the tiller means of the gasket includes ametal shim and a compressible layer of impregnated fibers in a laminatedstructure between two outer metal sheets, with the compressible layerbeing adhesively bonded to the adjacent outer metal sheet to preventlateral shifting therebetween.

In all of the above mentioned embodiments, the compressible section ofthe filler means has a maximum compressed thickness of 0.015 inch, andsurprisingly, such structures have sufficient compressibility to conformto head and block surfaces to provide a seal therebetween, while havingsuch a small amount of stress re laxation to substantially completelyeliminate the necessity of retorquing the cylinder head bolts once theyare tightened.

The binder with which the fibers of the filler sheets are impregnatedmay be a synthetic elastomer or a cured thermosetting resin. The type ofbinder preferred depends upon the kind of fibers used in the fillermeans. Although either type of binder may be used with any kind offiber, it is generally preferred to use an elastomer with asbestosfibers, and a resin with the other fibers that may be used for thefiller sheets.

Asbestos fibers are preferred for the filler sheets, but natural fibers,such as, for example, cotton or flax, or synthetic fibers, such as, forexample, nylon 7, may be used. With filler sheets having asbestosfibers, the binder, with which the fibers are impregnated, is preferablyneoprene, but other synthetic elastomers may be used.

When cotton, flax or nylon fibers are used for the filler sheets, it ispreferred to impregnate them with a thermosetting resin, such as, forexample, a phenolformaldehyde resin, melamine-formaldehyde resin, epoxyresin, etc. The filler sheets in which the fibers are impregnated with athermosetting resin are treated to cure the resin in accordance withconventional procedures. One example of a filler sheet of this type is anonwoven sheet of cotton fibers of uniform denier impregnated with acured phenol-formaldehyde resin, sold commercially by Spaulding FibreCompany under the designation of Spaulding No. 33. The resin impregnatedfiller sheet is non-wicking and is resistant to fluids and gases.

The gasket is provided with an aperture adapted to register with each ofthe cylinder bores, and with openings adapted to register with all theother openings provided in the cylinder block with which it is to beused. One of the outer metal sheets of the gasket, preferably the bottomsheet, is provided with upstanding flanges that define the perimeters ofeach of the apertures adapted to be aligned with the cylinder bores ofthe engine block with which the gasket is to be used. The filler meansof each embodiment includes at least one filler sheet having an edgeadjacent each of the upstanding flanges. When the gasket is assembled,the upstanding flange is bent downwardly to overlap the adjacent edge ofthe filler sheet and to form a metal protective surface at each edge ofthe gasket contiguous to said apertures.

In the embodiments having either a metal shim or a second filler sheetinterposed between the first mentioned filler sheet and the top metalsheet, the metal shim or the second filler sheet has its edge cut backfrom said apertures to allow room for the upstanding flange to be bentdownwardly against the top metal sheet without overlapping the edge ofthe metal shim or of the second filler sheet. The flanges are bentdownwardly to a uniform height, preferably by roller pressure. Theflanges are bent into contact with the top metal sheet, but are notpressed tightly against it. The rim portions of the gasket may bepressed downwardly until they are flush with the body portion, but it isprefered to have the rim portion project slightly above the body portionof the gasket until the gasket is compressed in its position of usebetween the cylinder block and head of an engine. In this manner,particularly in those embodiments utilizing a metal shim, a structure isprovided that has substantially uniform compressibility throughout itsarea.

The gasket is coated with a thermosetting resin in any suitable manner,as, for example, by roll coating or spraying, and is then treated tocure the resin. The surface coating of resin on the exposed faces of thegasket insures that the gasket will intimately and uniformly contact thecastings. The surface coating of resin also seals the edges of thegasket contiguous to the holes that are adapted to be aligned with thevarious holes in the cylinder block to make said edges liquid resistant.These edges do not have the metal protective surface that enables theedges of the gasket contiguous to the cylinder bores to withstand thehigh temperatures and pressures produced by fuel explosions in thecylinders, but are highly resistant to coolants, lubricants and fuelsbecause of the resin treatment.

Maximum sealing efficiency for the gasket is attained by compressing thegasket between the cylinder block and head to its minimum thicknessthroughout its area. When the gasket is positioned on a cylinder blockand the head is tightened in place, the pressure first compresses therim portions of the gasket until they are flush with the body portion ofthe gasket, unless the rim and body portions were flush initially.Thereafter, continued pressure compresses the rim and body portions ofthe gasket simultaneously. The rim portion forms a seal between theblock and head when it has been compressed to its minimum thickness.Accordingly, when the rim portions are compressed into sealingengagement, the seal is complete and extends throughout the area of thegasket.

By limiting gaskets formed in accordance with the present invention to amaximum compressed thickness of 0.030 inch, the performance of a typicalhigh compression is markedly improved. For example, when a gasket formedin accordance with the present invention having a thickness of0.028 inchis substituted for a typical prior art gasket having a thickness of0.052 inch in an engine having a compression ratio of 10:1, thecompression ratio is increased to l0.57:l. This very significant changein compression ratio results in better engine efficiency, higherhorsepower output, and improved gas mileage. Heretofore, those skilledin the art did not believe that gaskets as thin as those disclosedherein, i.e., less than 0.030 inch, and particularly wherein thecompressible section of the filler means of such gaskets have a maximumthickness of 0.015 inch, would be sufficiently compressible to form asatisfactory seal between a cylinder head and block. However, gaskets asdisclosed herein have not only functioned to effect a remarkedlyefficient seal, but also such gaskets have reduced torque loss of theassembly to a level which completely obviates the necessity ofretightening the head bolts after the gasket has been used for a periodof time.

The structure by means of which the above mentioned and other advantagesof the invention are attained will be described in the followingspecification, taken in conjunction with the accompanying drawingsshowing several embodiments of the invention,l in which:

FIG. 1 is a fragmentary top plan view of a gasket embodying theinvention, with portions thereof broken away to facilitate illustrationof the structure;

FIG. 2 is an enlarged fragmentary top plan view of a portion of thegasket contiguous to one of the cylinder bores, with portions brokenaway as in FIG. 1;

FIG. 3 is an enlarged cross-sectional view, taken along the line 3-3 ofFIG. 1;

FIG. 4 is a view similar to FIG. 3, showing another embodiment of theinvention;

FIG. 5 is a view, similar to FIG. 1, showing another embodiment of theinvention;

FIG. 6 is an enlarged cross-sectional view, taken along the line 6-6 ofFIG. 5;

FIG. 7 is a fragmentary top plan view of a further embodiment of theinvention;

FIG. 8 is an enlarged sectional view taken generally along line 8-8 ofFIG. 7; and

FIG. 9 is an enlarged top perspective view looking generally in thedirection of line 8-8 of FIG. 7.

In the embodiment of the invention shown in FIGS. 1 to 3 of thedrawings, gasket 11 comprises a thin sheet 12 of cold rolled steel,preferably tin plated, forming the bottom layer of the gasket, a secondthin sheet 13 of similar steel forming the top layer of the gasket, abottom filler sheet 14 and a top filler sheet 15. All four sheets areapproximately coextensive in area and are provided with a plurality ofaligned apertures 16 adapted to register with the cylinder bores in thecylinder block on which the gasket is to be seated in use. All foursheets are also provided with openings to register with each of theopenings provided in the cylinder block, such as, for example, screw orbolt holes.

The filler means comprises two sheets which may be woven or nonwoven,and are preferably made of nonwoven cotton fibers, but may be made ofother natural fibers, such as flax, for example, or synthetic fibers,such as nylon 7, for example, which are highly resistant todisintegration by heat. These characteristics of the fibers help to makethe gasket capable of withstanding the temperature and pressureconditions encountered by it when it is used in a high compressionengine. A layer of fibers is impregnated with thermosetting resin,suitably a phenol'formaldehyde resin, melamineformaldehyde resin, epoxyresin, etc., to form a flller sheet that is then treated to cure theresin. The filler sheet is resistant to fluids and gases, isnon-wicking, and will not flow or disintegrate under heat and pressureconditions that normally exist in a high compression engine duringoperation of the engine. In use, the tiller sheets are compressiblewithout being subject to lateral deformation either under pressurealone, or under heat and pressure. p

The impregnation of the layer of fibers with the resin enables thefiller sheets to have a calendered finish which makes it possible tocontrol the thickness of the filler sheet with precision and to form avery thin sheet of uniform thickness throughout its area. A gaskethaving a total thickness in excess of 0.030 inch is not commerciallydesirable for use in sealing the cylinder bores of high compressionautomobile engines. In one embodiment of the invention, the fillersheets are each preferably 0.007 inch thick, but may have any thicknesswithin the range of from 0.0065 to 0.0075 inch, with the maximumthickness of the compressible filler means being 0.015 inch. The outermetal sheets preferably have a thickness of 0.006 inch, but may be ofany thickness within the range of from 0.0055 to 0.007 inch. In thisgasket, each filler sheet is approximately 0.001 inch thicker than eachmetal sheet. This difference in thickness between the tiller sheets andthe metal sheets makes the body portion of the gasket approximately0.001 inch thicker than the rim portion and provides an effective sealover the entire area of the gasket when the gasket is compressed in theposition in which it is used. A gasket comprising two filler sheets andtwo outer metal sheets of the thicknesses specified above will notexceed the 0.030 inch limit of commercial acceptance for gaskets to beused in high compression automobile engines.

As shown best in FIG. 3, the bottom metal sheet has an upstanding flange17 forming aperture 16 that is adapted to be aligned with one of thecylinder bores of the engine block on which the gasket is to be used.The bottom filler sheet is cut in such a manner that the edge 18 isadjacent one surface of the upstanding flange. The corresponding edge 19of the top filler sheet is spaced from the aperture far enough to allowthe flange to be bent downwardly without overlapping it. The flange 17is bent downwardly over the edge of the top metal sheet to provide ametal overlap in the form of an annular rim 20 surrounding the aperture.The flange also provides the gasket with a metal protective surface atthe edge of the cylinder bore which enables the gasket to with stand thehigh temperatures and pressures produced by fuel explosions in thecylinders.

Flanges 17 are roll flattened to depress the rim to a uniform extent,but the pressure applied is not sufficient to press the rims tightlyagainst the top metal sheet, with the result that rims 20 project aslight distance above the top metal sheet before the gasket is securedin place between the cylinder block and the head of the engine in whichit is to be used. The gasket is coated with thermosetting resin by rollcoating or spraying, and is then treated to cure the resin. The surfacecoating of resin on the exposed faces of the gasket insures that thegasket will have a uniform intimate contact with the castings betweenwhich the gasket is positioned. The resin coating also seals the edgesof the gasket contiguous to the holes that are not provided with themetal protective surfaces provided by flanges 17 adjacent apertures 16.

When the cylinder head is secured to the block, the pressure is appliedfirst against rims 20, following which the entire gasket is compresseduntil the rim portions reach their minimum thickness and prevent anyfurther flattening action. The width of the annular rim 20 is less thanthe lateral distance between flange l7 and the adjacent edge of the topfiller sheet. when the gasket is compressed, rim 20 fits into theannular space between flange 17 and edge 19, and edge portion 21 of thetop metal sheet is pressed downwardly against the upper surface of thebottom filler to form a rim portion comprising three thicknesses ofmetal and one thickness of the lower flller sheet.

The entire gasket is compressed to uniform thickness, but the bodyportion of the gasket is thicker than the minimum thickness of the rimportion because it includes the additional thickness of the upper fillersheet over the thickness of metal rim 20. Thus, the

body portion of the gasket is compressed into sealing engagement betweenthe cylinder block and the head when the rim portion is compressed toits minimum thickness.

In the embodiment of the invention shown in FIG. 4, the outer metalsheets of the gasket are identical to the embodiment of FIGS. 1 to 3,and will be identified by the same reference numerals. The tiller meansof this embodiment comprises a sheet 22 of fibers highly resistant toheat, as, for example, asbestos, and a thin metal shim 23 positionedbetween the upper surface of sheet 22 and upper metal sheet 13. As inthe embodiment of FIGS. 1 to 3, outer metal sheets 12 and 13 are ofuniform thickness within a range of from 0.0055 to 0.007 inch. Metalshim 23 is also uniform in thickness within the same range as the outermetal sheets.

The asbestos fibers are impregnated with a binder, suitably a syntheticelastomer, such as, for example, neoprene, and formed into sheets ofapproximately the same thickness as the thickness of the filler sheetsof the embodiment of FIGS. 1 to 3. A sheet 22 is positioned on the uppersurface of bottom metal sheet 12 with its edges 24 adjacent flanges 17.A metal shim 23 is positioned on the upper surface of sheet 22 with itsedges 25 corresponding to edges 24 of sheet 22, spaced inwardly fromedges 24 a sufficient distance to allow flange 17 to be bent downwardlywithout overlapping them. Upper metal sheet 13 is positioned on top ofmetal shim 23, the flange 17 is bent inwardly and downwardly over theadjacent edges portion 21 of upper metal plate 13 to from a rim clampingthe upper metal plate and the metal shim in place. When the head istightened against the engine blcok, rim 20 is moved downwardly until itis flush with the upper surface of outer metal sheet 13. Continueddownward pressure forces plate 13 and rim 20 downwardly until the rimportions reach their minimum thickness. As plate 13 is being forceddownwardly, sheet 22 is compressed to a uniform thickness within thedesired range of from .0065 to 0.0075 inch, thus providing a gaskethaving filler means comprising a sheet of asbestos fibers with a totaloverall thickness less than 0.030 inch. In the embodiment of FIG. 4,with the edge of each flange 20 being substantially in alignment withthe edge 25 of the shim openings, it will be appreciated that asubstantially uniform thickness of metal is provided throughout thegasket, so that the gasket has uniform compressibility characteristics.

In the embodiment of FIGS. 5 and 6, a gasket 26 comprises a singlefiller sheet 27, similar to either filler sheet 14, or 22, sandwichedbetween two thin outer metal sheets 28 and 29. Gasket 26 has apertures30 adapted to be aligned with the cylinder bores of the engine block andvarious other openings 31 for bolts, lubricants, coolants, etc. Fillersheet 27 is additionally apertured, as indicated at 32, in a pluralityof spaced areas near the outer edges of the gasket for a purposehereinafter disclosed.

The edges 33 of bottom metal sheet 28 adjacent apertures 30 are bentupwardly and then reversely to form rims 36 overlapping edges 34 offiller sheets 27. The upper surface of rims 36 is flush with the uppersurface of top metal sheet 29 and the gap between edges 33 and is veryshort.

As shown in FIG. 6, metal sheets 28 and 29 are indented, as indicated at37 and 38, respectively, in the area of each aperture 32, to providemetal-to-metal contact between the outer metal sheets through eachaperture 32. Metal sheets 28 and 29 are secured together permanently inthe area of each aperture 32 by welding, or in any other suitablemanner. Instead of indenting both metal sheets, as shown at 37 and 38,an indentation of twice the depth shown may be provided on one metalsheet, and the other metal sheet may be flat.

With the structures of FIGS. 5 and 6, the welds are spaced closelyenough to cause upper metal sheet 29 to compress the fibers of sheet 27to uniform thickness throughout the surface area of the gasket.

In the embodiment of FIGS. 7-9, the gasket is indicated in its entiretyat 40, and includes filler means 41 sandwiched between an upper metalsheet 42 and a lower metal sheet 43. The filler means 41 is defined by acompressible layer 44 of asbestos fibers impregnated with a latex binderand a metal shim insert 45. As is evident from FIG. 8, the shim 45terminates at 45a a substantial distance outwardly of the cylinderopenings. As can also be best seen in FIG. 8, the top sheet 42 isperforated at a plurality of spaced locations to provide curvedprojections 46 that extend downwardly through the compressible layer 44.As in the previous embodiments, the lower sheet 43 is reversely bent atthe cylinder openings to provide an outwardly facing annular portion 43aaround the cylinder openings so that a sub stantially uniform amount ofmetal is present throughout the gasket.

In an exemplary embodiment, the top layer 42 is formed of steel having athickness of 0.006 inch, and the bottom layer 43 is formed of tin platedsteel having a thickness of 0.0083 inch. The increased thickness of thebottom layer provides an increased measure of protection about thecylinder openings. The shim insert 45 is also formed of steel and has athickness of 0.006 inch in the exemplary embodiment. The asbestos layer44 has an initial .uncompressed thickness in the range of 0012-0015inch, and the composite gasket structure is compressed to a thicknessnot greater than 0.030 inch.

The gasket 40 of FIGS. 7-9 may be convenientlyformed by firstperforating the top layer 42 to form the projections 46, and then rollcombining the asbestos layer 44 with the upper sheet 42, such that theprojections 46 interlock the asbestos layer with the upper layer. As analternative to the mechanical interlock provided by projections 46, orsupplementary thereto, the asbestos layer.44 may be adhesively securedto the upper layer 42. In the event that asbestos layer 44 is secured tometal layer 42 by adhesive alone, the adhesive is preferably applied tothe metal layer 42 by a roller, or the like; and the asbestos layer issubsequently joined to the coated metal between the nip of a pair ofrollers, or other suitable combining means.

Suitable adhesives for adhering the metal layer 42 to the asbestos layer44 are known in the art. Adhesives forming oil-resistant bonds arepreferred in one suitable adhesive system comprising a mixture of anatural resin and a synthetic oil-resistant elastomer dispersed in aliquid solvent or dispersant. Suitable natural rosins may be derivedfrom woods and asphalt and include rosins, pitches, bitumens andlow-molecular oil resins in aqueous emulsions or organic solventsolutions. Suitable oil-resistant elastomers include polysulfide(Thiokol) and nitrile elastomers in aqueous latices or organic solventsolutions.

After the asbestos layer 44 has ben combined with the upper layer 42,the resulting structure is die cut as a unit to providethe cylinderopenings, the coolant openings and the bolt holes. The shim 45 is thendie cut separately to provide the bolt holes, coolant opening andenlarged cylinder openings. The bottom layer 42 is then blanked andformed at the cylinder bores, and the shim 45 and composite upper layer42 and asbestos layer 44 are then placed upon the lower layer 43. Thecylinder bore overlapping portions 43 are then rolled downwardly tocomplete the sandwich structure, and the finished gasket is coated witha synthetic resin to achieve a surface seal between the gasket faces andthe adjacent casting surfaces.

In order to show the markedly improved torque retention characteristicsof gaskets formedin accordance with the teachings of the presentinvention, comparative tests were run on an Instron testing machineModel No. TTD, available from lnstron Corp., 2500 Washington Street,Canton, Mass. The results of these tests are tabulated herebelow.

TABLE I Overall Thick- Thickness ness of Compres- Com- Comas mfg.Compression pressed pressi- Gasket in mils sible in mils ThickbilityLayer ness l 73 50-55 9.8 72.2 13.4 72.5 50-55 10.4 72.1 14.35 2 70.050-55 8.9 61.1 12.7 71.0 50-55 10.0 61.0 14.1 3 51.0 30 7.7 43.3 15.151.0 30 7.7 43.3 15.1 4 46.0 40 5.7 40.3 12.4 46.0 40 5.8 40.2 12.6 534/0 30 4.2 29.8 12.4 34.0 30 4.3 29.7 12.6 6 49.0 40 9.7 39.3 19.8 49.040 10.4 38.6 21.2 7 32.0 12-15 2.9 29.1 9.1 32.0 l2-l5 2.9 29.1 9.1 832.0 12-l5 3.0 29.0 9.4 32.0 12-15 3.1 28.9 9.7

Gaskets 1-6 are common gaskets that are commercially available, andgaskets 7 and 8 were formed in accordance with the teachings of thepresent invention. Gasket 1 includes an asbestos filler layer of 50-55mils sandwiched between upper and lower copper layers 9 mils thick.Gasket 2 ineludes an asbestos filler layer 50-55 mils thick sandwichedbetween an upper 7 mil tin plate steel layer and a lower 10 mil tinplate steel bottom layer. Gasket 3 includes a 6 mil perforated steelcore having mil asbestos layers on opposite sides thereof, with a 6 milsteel bottom layer being wrapped around the upper asbestos layer at thecombustion openings. Gasket 4 includes a 7 mil upset metal core havingmil asbestos faces on opposite sides thereof. Gasket 5 includes a 7 milupset metal core having 15 mil asbestos faces at opposite sides thereof.Gasket 6 includes a 7 mil perferated steel core having 20 mil asbestosfaces at opposite sides thereof.

Gaskets 7 and 8 are similar to that illustrated in F IG. 4 of thedrawing, and include a filler means having a 12-15 mil asbestos layerand a 6 mil cut back steel shim sandwiched between a 6 mil steel toplayer and an 8.3 mil steel bottom layer. As is evident from thecompressibillty column in Table l, gaskets 7 and 8 have a substantiallower compressibility than the other gaskets that were tested. Since theamount of compressibility is directly proportional to the amount ofstress relaxation in the gasket, and hence inversely proportional to thetorque retaining ability of the gasket, gaskets 7 and 8 have vastlysuperior torque retention characteristics.

in order to further substantiate the improved torque retentioncapabilities of the gaskets of the present invention, several gasketswere tested in a high compression 292 horsepower Ford V-8 that was runfor an extended period hours). A standard procedure in the gasketindustry was employed to measure retained torque in the cylinder boltsand this test involved scribing a sharp line on the head bolts and thecylinder head at the conclusion of the engine operational test, and thenloosening the head bolts at least one-quarter turn. The bolts were thenretightened with a calibrated torque wrench until the lines on the boltsand the cylinder head coincide and the torque reading at this time wasthen recorded. The results of these tests are tabulated herebelow TABLEll Torque Loss Torque Loss Average Average Gasket Lb.-Ft. l I 21 30 2130 2 32 46 3 34 49 4 14 20 12 17 Gaskets 1-3 are common gaskets that arecommercially available, and gaskets 4 were formed in accordance with theteachings of the present invention. Gasket 1 consists of a 7 mil upsetmetal core with 20 mil asbestos faces on opposite sides thereof. Gasket2 consists of a 21 mil asbestos billboard filler layer with an 8 mil tinplat steel top layer and a 10 mil tin plate steel bottom layer. Gasket 3includes a 6 mil perforated steel core with 25 mil asbestos layers onboth faces thereof.

Gaskets 4 are similar to those illustrated in FIG. 4 of the drawings,and include filler means of 12-15 mil asbestos layer, and a 6 mil cutback tin plate steel shim sandwiched between a 6 mil tin plate steel toplayer and a 8 mil tin plate steel bottom layer. As is evident from thetorque loss figures in Table 11, the gaskets formed in accordance withthe present invention have much higher torque retention characteristics,and in fact obviate the necessity of retorquing which is necessary inother gaskets having a compressible filler means greater than 0.015 inchin order to maintain a proper seal between the cylinder head and theblock.

Although preferred embodiments of the invention have been described inconsiderable detail, it will be understood that the description thereofis intended to be illustrative, rather than restrictive, as many detailsof construction may be; modified or changed without departing from thespirit or scope of the invention. Accordingly, it is not desired to berestricted to the exact construction described.

What is claimed is:

l. A compressible gasket for sealing the cylinder bore of a highcompression automobile engine and capable of maintaining its dimensionalstability under the temperature and pressure conditions encountered inuse in such an engine, said gasket having a total compressed thicknessof less than .030 inch and comprising two outer metal sheets and fillermeans sandwiched between said metal sheets, said metal sheets and saidfiller means each having apertures in registration with one another,including combustion openings, and each lamina having generally parallelplanar faces whereby each lamina is of substantially uniform thickness,said filler means including a compressible layer comprised of asbestosfibers impregnated with a binder and having a maximum compressedthickness of 0.015 inch, said filler means also including a single metalshim between said layer of fibers and one of said sheets, at least someof the apertures in said shim at said combustion openings being spacedconcentrically outwardly of the registering apertures in said layer offibers, one of said sheets having first portions extending through saidlast mentioned apertures and second reversely bent 'portions extendingoutwardly into a position substantially vertically aligned with lastmentioned shim apertures whereby a four layer laminate is providedaround said combustion openings including a double thickness of said onemetal sheet, a single thickness of the other of said metal sheets, andsaid compressible layer thereby providing substantially uniformcompressibility characteristics throughout said gasket, the exposedsurfaces of said gasket being coated to provide a means for insuringthat the gasket will intimately and uniformly contact the facingsurfaces of a cylinder head and block.

2. A compressible gasket as set forth in claim I ineluding means,cooperating with one of said metal sheets and said layer of non-metallicfibers, for preventing said layer of non-metallic fibers from movingrelative to said one metal sheet.

3. A compressible gasket as set forth in claim 2 wherein said movementpreventing means includes bonding media connecting said one metal sheetto said layer of non-metallic fibers at least over a portion of theinterface between said one metal sheet and said layer of non-metallicfibers.

4. A compressible gasket as set forth in claim 3 wherein said bondingmedia includes outwardly struck portions of said one metal sheet thatare embedded in said layer of non-metallic fibers.

5. A compressible gasket as set forth in claim 3 wherein said bondingmedia includes adhesive means interposed between said one metal sheetand said layer of non-metallic fibers.

V UNIT D sm'ifnis PATENT 'omcr, e

H CERTIFICATEUF CORREC'HON e Patent 80. 3,,738l558 A Dated June 12,1.973- M lnueutyhs) otha Leroy Colwell I I: is certified that errornppeara in the nbovmidcntified patent and that seld Letters intun t arehereby eerrected as shown below:

601. l, line 6 av-ohdis" should be avoids 3 Col. 2, line "1h" (secondoccur r enee) .should be is A A Col. 4, lines 4 end 5 "pr efered" shouldbe preferred Col. 6, line 56, "when" should be when a I A Col. 7, line29, "the should be and A line 30, "edges" should be edge l i ne 31,'"from" should be A fofm --'5 A line 33, "block" should be bloek line61, "sheets" should be sheet e01. 8;.11ne 19; the g 1n "u5a", should beitalicized;-

line 54 after "metal" insert layer";

line "pei-ferated" should be perforated 5- Col. 1O,- line after. "V- S'insert engine --;V

Signed and sealed this 26th day of March 1974.

(SEAL) Attest:

EDWARD MgFLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. A compressible gasket for sealing the cylinder bore of a highcompression automobile engine and capable of maintaining its dimensionalstability under the temperature and pressure conditions encountered inuse in such an engine, said gasket having a total compressed thicknessof less than .030 inch and comprising two outer metal sheets and fillermeans sandwiched between said metal sheets, said metal sheets and saidfiller means each having apertures in registration with one another,including combustion openings, and each lamina having generally parallelplanar faces whereby each lamina is of substantially uniform thickness,said filler means including a compressible layer comprised of asbestosfibers impregnated with a binder and having a maximum compressedthickness of 0.015 inch, said filler means also including a single metalshim between said layer of fibers and one of said sheets, at least someof the apertures in said shim at said combustion openings being spacedconcentrically outwardly of the registering apertures in said layer offibers, one of said sheets having first portions extending through saidlast mentioned apertures and second reversely bent portions extendingoutwardly into a position substantially vertically aligned with lastmentioned shim apertures whereby a four layer laminate is providedaround said combustion openings including a double thickness of said onemetal sheet, a single thickness of the other of said metal sheets, andsaid compressible layer thereby providing substantially uniformcompressibility characteristics throughout said gasket, the exposedsurfaces of said gasket being coated to provide a means for insuringthat the gasket will intimately and uniformly contact the facingsurfaces of a cylinder head and block.
 2. A compressible gasket as setforth in claim 1 including means, cooperating with one of said metalsheets and said layer of non-metallic fibers, for preventing said layerof non-metallic fibers from moving relative to said one metal sheet. 3.A compressible gasket as set forth in claim 2 wherein said movementpreventing means includes bonding media connecting said one metal sheetto said layer of non-metallic fibers at least over a portion of theinterface between said one metal sheet and said layer of non-metallicfibers.
 4. A compressible gasket as set forth in claim 3 wherein saidbonding media includes outwardly struck portions of said one metal sheetthat are embedded in said layer of non-metallic fibers.
 5. Acompressible gasket as set forth in claim 3 wherein said bonding mediaincludes adhesive means interposed between said one metal sheet and saidlayer of non-metallic fibers.